High quality foam was developed as a premium cost fracturing fluid in the past decade, but many beneficial properties of foam may make it the fluid of choice for hydraulic fracturing in the 1990's.

Foam fluids were first applied to gas reservoirs having low pressure, since gas in the foam expanded after the treatment to remove the fracturing fluid from the well, minimizing damage to the formation. But foams have also been applied to all types of wells, low or high pressure, gas or oil, where it was important to minimize damage. The low liquid content of foams leaves less liquid to remove from the well.

Foam fluids have low fluid loss to the formation. In addition, the gel filtercake which is deposited on the formation face during fracturing is substantially thinner than filter cakes deposited by other fluid types such as crosslinked polymer fluids. Damage to fracture conductivity is minimized.

The two-phase structure of foam fluids allows the generation of high viscosity fluids for fracture propagation, and its yield point characteristics provide enhanced proppant transport. Mathematical relations can calculate the foam composition required for specific applications over a broad range of gas qualities, temperatures, and polymer concentrations.

The development and application of constant internal phase design concepts allow proppant to be added to a foam fluid while maintaining viscosity constant. High proppant concentrations can be carried with constant internal phase foams while minimizing frictional pressure losses.

This paper discusses the relationships of rheology, fluid loss, constant internal phase design, and fluid recovery in application of foam to hydraulic fracturing.

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